Known glazing comprises the standard transparent glazing, which gives rise to specular transmission and reflection of radiation incident on the glazing, and translucent glazing, which give rise to diffuse transmission and reflection of radiation incident on the glazing.
Usually, reflection by glazing is called diffuse when radiation incident on the glazing at a given angle of incidence is reflected by the glazing in a plurality of directions. Reflection by glazing is called specular when radiation incident on the glazing at a given angle of incidence is reflected by the glazing at an angle of reflection approximately equal to the angle of incidence. Similarly, transmission through glazing is called specular when radiation incident on the glazing at a given angle of incidence is transmitted by the glazing at an angle of transmission approximately equal to the angle of incidence.
A projection screen comprises two faces or main surfaces, namely a first face on which the image is projected that comes from the light source positioned in the same region of space as the light source (direct projection) and a second opposite face on which the image projected on the first face optionally appears by transparency.
A back projection screen has a first face and a second opposite face possessing the same characteristics as those of the aforementioned projection screens. However, a back projection screen differs from a projection screen in that the user and the light source are not located in the same region of space but are on either side of the screen. Back projection involves placing the projector behind the glazing.
Hereinafter, unless stated otherwise, the term “projection” is used in a general way to denote both projection and back projection.
It is not conceivable to use transparent standard glazing as projection screens. In fact, this glazing does not have the property of diffuse reflection, and therefore does not allow images to be formed on any one of its faces and throws back reflections just like a mirror.
There have been many attempts to endow transparent standard glazing with additional properties allowing use thereof as a projection screen, while maintaining a clear view through the glazing.
WO 2013/175129 A1 describes glazing comprising a transparent layered element with properties of diffuse reflection allowing the projection of images, visible at a large viewing angle, while maintaining transparency of the glazing. However, it has been found that with such glazing, in certain conditions of use, in particular when the luminous contrast is not sufficiently pronounced between the two sides of the glazing, an observer positioned on the less luminous side perceives an impression of blurring or of “milky glazing” which limits the clarity of view. For certain applications, in particular in the automotive sector, this blurred and milky appearance, even if slight, may be regarded as unacceptable in viewing zones.
It is these drawbacks that the invention intends more particularly to overcome, by proposing transparent glazing that allows projection of images and that satisfies the criteria of clear vision stipulated in particular in the field of transport, while having a uniform overall appearance.